Switch rendering engine depending on render layer?
You should use different scenes for each renderer. On the top toolbar next to where you select your render engine you can find to the left the scenes. Add a new scene and switch to the appropriate render engine.

1.

Rename the current scene to the render engine's name

2.

Create a Link Object Data copy of the current scene



3.

Rename it the other render engine and selected the render engine from the drop down to the right.